Silver halide element containing a developer and aromatic sulfinic acid stabilizers



United States Patent 3,466,173 SILVER HALIDE ELEMENT CONTAINING A DE- VELOPER AND AROMATIC SULFINIC ACID STABILIZERS Hidehiko Ishikawa, Odawara-shi, Mikio Sato, Kanagawaken, and Kazuo Matsui, Tokyo, Japan, assignors to Keulfel & Esser Company, Hoboken, N.J., a corporation of New Jersey No Drawing. Filed Nov. 29, 1966, Ser. No. 597,567 Claims priority, application Japan, Nov. 30, 1965, 40/725,178 Int. Cl. G03c 1/48; G03c 1/34 US. CI. 96-95 6 Claims ABSTRACT OF THE DISCLOSURE Incorporation of an aromatic sulfinic acid derivative into direct positive photographic material including a photographic developer provides extended storage capabilities.

This invention relates to a direct positive, photographic silver halide material utilizing the Herschel effect and which contains a developing agent and can be quickly treated according to a stabilizing process. An object of the present invention is to provide a direct positive, photographic material of improved storage stability which can provide stable copies of graphic originals by means of simple processing.

As is well known, a direct positive light-sensitive silver halide material utilizing the Herschel effect has in the emulsion a silver halide which has been fogged by light or chemical procedure, and can directly form a positive image by single yellow light exposure and subsequent developing treatment. Further, it can be safely handled even under common incadescent light. By virtue of the above advantages, such material is widely utilized for the preparation of intermediate masters of such documents as plans of shipbuilding or civil engineering and maps of aerial survey and the like.

The development of permanent images utilizing direct positive, light-sensitive material, however, is particularly complex, since numerous steps of development, fixing, and washing are usually required and are notably time consuming. Further, the developing solution suffers, during continuous use, from variation in concentration and deterioration in developing ability which, coupled with an incomplete water-washing treatment, cause great difiiculties in forming a clear, stable image.

Direct positive, light-sensitive materials are known which provide rapid development of images by the stabilizing process. Such materials include a developing agent in the emulsion layer of the light-sensitive material. The material, after exposure, is developed in an alkali bath comprising caustic soda or sodium carbonate and is then treated in a stabilizing bath comprising a fixative such as ammonium thiocyanate or the like. However, when the stabilizing process is directly applied to a direct positive, light-sensitive material utilizing Herschel effect, i.e. when a developing agent is incorporated into the fogged emulsion, the fogged silver halide contained therein is destroyed by the developing agent either shortly after preparation of the emulsion or during storage after application of the emulsion to a support, and it is therefore extremely difiicult to obtain a useful product. Even in the case where a layer is provided separate from the emulsion layer of a light-sensitive material and a developing agent is incorporated in the separate layer in an attempt to prevent contact between the fogged silver halide crystals and the developing agent, the fogged silver halide 3,466,173 Patented Sept. 9, 1969 is destroyed during storage, and a product of acceptable storage stability is difliculty obtainable.

Now, according to the present invention there has been produced a direct positive, light-sensitive material which is excellent in storability and can be quickly treated according to the stabilizing process and which suffers from no decomposition of fogged silver halide even during a long time storage at high temperature and humidity. Such improved material is prepared by incorporating in the emulsion layer containing fogged silver halide a developing agent, such as hydroquinone or l-phenyl-3-pyrazolidone, and an aromatic sulfinic acid or its salt (hereinafter referred to as sulfinic acid).

The direct positive, light-sensitive material according to the present invention may be variously prepared, for example, a sulfinic acid may be included with a developer in the emulsion layer, a layer comprising a developing agent may be separately provided adjacent the emulsion layer, including a sulfinic acid or a developing agent and a sulfinic acid may be incorporated into a layer provided adjacent the emulsion layer.

Even when incorporated into the fogged silver halidecontaining emulsion layer of a direct positive light-sensitive material, the sulfinic acid employed in the present invention effectively prevents the destruction of fogged silver halide crystals otherwise occurring due to the presence of a developing agent, without contaminating the emulsion layer or injuring the photographic efliciency of the material. The amount of the acid to be added is preferably about 20 by weight of the developing agent employed. This ratio is not critical, however, and may be varied to a substantial degree. The acid may be added in the form of a solution in water or lower alcohol or in a mixed solution thereof. Similarly, when it is to be added together with a developing agent. The thus prepared solution may be added any time after preparation of the emulsion, though it is preferable to add it immediately before application of the emulsion to a support.

Typical of the sulfinic acids and their salts employed in the present invention are as shown below, but these arenot limitative.

( 1) Benzenesulfinic acid (2) Para-toluenesulfinic acid (3) Para-chlorobenzenesulfinic acid (4) Para-formylbenzenesulfinic acid (5) N apthalenesulfinic acid Useful salts of the sulfinic acids are water-soluble salts such as sodium salts and potassium salts.

A is clear from the above, the present invention is a direct positive, light-sensitive silver halide material, in which a developing agent as well as a sulfinic acid or its salt are incorporated in the emulsion layer or in a layer provided adjacent the emulsion layer. The destruction of fog nucleus heretofore resulting from the presence of the developing agent is prevented by the sulfinic acid or its salt. The light-sensitive material of the present invention is excellent in storability for a long period of time and at high temperature and humidity, and can quickly form a positive image by application of the stabilizing process, i.e. by developing in an alkaline bath and then treating in a stabilizing bath comprising ammonium thiocyanate or the like.

The following examples illustrate the present invention.

Example 1 30 cc. of a 6% aqueous sodium metaborate solution was added to 1 kg. of a pure silver chloride emulsion containing 40 g. of silver nitrate, and the pH of the mixture was adjusted to 8.5. To the mixture was added 7 cc. of a 3 aqueous formaline solution, and the resulting emulsion was heated at 40 C. for 30 minutes to form a fog nucleus. This emulsion was adjusted to pH 6.0 by addition of a aqueous citric acid solution. To the emulsion were added 60 cc. of a 0.1% aqueous Pinakryptol Yellow solution and 200 cc. of a solution of the following composition:

Methyl alcohol cc 100 Hydroquinone g 30 Sodium salt of para-toluenesulfinic acid g 5.0 Water to make cc 200 The thus obtained emulsion was coated on a photographic paper so that the amount of silver per square meter was 1.5 g. and was ten dried to prepare a sample.

As a counter-example, an emulsion obtained under the same conditions as above, except that the sodium salt of the sulfinic acid was not used, was coated on a photographic paper and was then dried to prepare a control sample.

The above two examples were exposed, both immediately after drying and after allowing to stand for 3 months, through a common yellow filter in the manner usually employed with Herschel effect photographic papers. Subsequently, the samples were treated for 4 seconds in an alkali bath containing 20 g, of anhydrous sodium sulfite and 40 g. of caustic soda in one liter of water and then for an additional 4 seconds in a stabilizing bath containing 200 g. of ammonium thiocyanate in one liter of water. Thereafter, the maximum image densities of the samples were measured to obtain the results as shown in Table 1.

The fog nucleus was only slightly effected in the case of the invention material after allowing to stand for 3 months, but was greatly destroyed in the case of the control sample.

Example 2 A developing solution was prepared by adding to 1 kg. of a 4% aqueous gelatine solution 100 cc. of a solution of the following composition:

Methyl alcohol cc 60 Hydroquinone -g Sodium pyrophosphite g 0.5 Para-chlorobenzenesulfinic acid g" 5.0 Water to make cc 100 The solution was coated on a photographic paper so that 0.8 g. of the hydroquinone was contained per square meter of the paper and was then dried.

As a counter-example, the same solution as above, except that the sulfinic acid was not included, was coated on a photographic paper under the same condition as above and was then dried.

Onto each of the above two coatings was applied a fogged emulsion which had been controlled in pH and included Pinakryptol Yellow as the emulsion prepared in Example 1. Both immediately after drying and after allowing to stand for 48 hours at a temperature of 50 C. and relative humidity of 80%, the two samples thus prepared were subjected to exposure, development, and stabilizing as in Example 1, and then the maximum image densities thereof were measured to obtain the results as shown in Table 2.

TABLE 2 Maximum image density Inunetliately After 48 hours after drying forced aging Sample of the present invention 1.50 1. 35 Control sample 1. 50 0. G0

15 g. of hydroquione and 0.5 g. of sodium pyrophosphite were dissolved in 1 kg. of a 4% aqueous gelatine solution. The solution was coated on a photographic paper so that 0.8 g. of the hydroquinone was contained per square meter of the paper, and was then dried to form a layer. Onto this layer a fogged emulsion, prepared as in Example 1, was applied to prepare a control sample. On the other hand, a sample according to the present invention was prepared by coating on the developer layer the emulsion of Example 1 including 200 cc. of a solution of the following composition:

Methyl alcohol cc 100 Potassium salt of benzenesulfinic acid g 5.0 Water to make cc 200 Both immediately after drying and after allowing to stand for 48 hours at a temperature of 50 C. and a relative humidity of the above two samples were exposed, developed, and stabilized as in Example 1, and

,- then the maximum image densities of the samples were measured to obtain the results as shown in Table 3.

TABLE 3 Maximum image density Immediately After 48 hour? The fog nucleus was greatly destroyed, by the forced aging, in the case of the control sample, but was stable in the case of the sample of the present invention.

The above examples have been presented for the purpose of illustration and should not be taken to limit the scope of the present invention. It will be apparent that the described examples are capable of many variations and modifications which are likewise to be included Within the scope of the present invention as set forth in the appended claims.

What is claimed is:

1. A direct positive photographic material comprising a support bearing a substantially dry coating comprising:

(a) a fogged Herschel silver halide emulsion layer;

(b) a photographic developer; and

(c) a stabilizer selected from the group consisting of aromatic sulfinic acids and Water soluble salts thereof.

2. Material according to claim 1 wherein said developer and said stabilizer are intimately uniformly distributed throughout said emulsion layer.

3. Material according to claim 1 wherein said stabilizer is uniformly distributed throughout and emulsion layer and said developer is included in a layer adjacent said emulsion layer.

4. Material according to claim 1 wherein said stabilizer and said developer are intimately distributed throughout a layer adjacent said emulsion layer.

5. Material according to claim 1 wherein said stabilizer is selected from the group consisting of benzenesulfinic acid, para-toluenesulfinic acid, para-chlorobenzenesulfinic acid, para-f0rmylbenzenesulfinic acid, naphthalenesulfinic acid, and water-soluble salts of said acids.

5 6 6. Material according to claim 1 wherein said stabilizer 2,983,610 5/1961 Allen et al. 96-108 is present in an amount of between about 15-30% by 3,062,651 11/1962 Hillson 96-95 weight of said developer. 3,144,336 8/1964 Herz 96-108 3,248,219 4/1966 Jacobs 96-95 XR uNlTE g g zl lfl is gfTENTs 5 NORMAN G. TORCHIN, Primary Examiner MARY F. KELLEY, Assistant Examiner 2,057,764 10/1936 Brunken 96-109 XR U'S CLX.R 2,098,442 11/ 1937 Troland 96-94 XR 2,983,609 5/1961 Allen et a1 96-108 XR 10 96 10\9 

